Nobles and Infils simply do not mix in my mind. Sneak into a vault to rob it? Burn food without being noticed? Stab someone when he sleeps? It looks way too much like a commoner's job.
The problem is that making the adventurers infiltrators, even if much poorer ones, would change a lot the dynamic of the game. It would be interesting, in a way, for it would cost them much more to raise their skills by themselves, and a noble could fund them, but it would be an expensive bet since if he gets caught doing infil job he gets auto-hanged. And it should be only experienced advies to avoid infil spam? Meh, still doesn't sound good enough.
